Thermostat.



No. 748,323. PATENTED DEC. 29, 1903.

G. A. WALL.

THERMOSTAT.

APPLICATION FILED OOT.28,1902.

N0 MODEL.

HEAT INS (H4 01? Zfdrzeasea: Invent?) M Z WW Patented December 29, 1908.

PATENT OFFICE.

GEORGE AUGUSTUS WALL, OF PROVIDENCE, RHODE ISLAND.

THERMOSTAT.

SPECIFICATION forming part of Letters Patent No. 748,323, dated December29, 1903.

Application filed October 28, 1902. Serial No. 129,134. (No model.

To all whom it may concern.-

Be it known that I, GEORGE AUGUSTUS WALL, of Providence, in the countyof Providence and State of Rhode Island, have invented a new and usefulThermostat, of which the following is a specification.

The object of my invention is to prod nee a simple thermostat which iscertain to operate on a given rise of temperature, is very simple,inexpensive, durable, easily refitted for a second use, and adaptedgenerally for all uses for which a thermostat is desirable; and

my invention consists in a thermostat made up of a spiral spring, twoplates or disks of metal, and a flat film of solder holding the twoplates fiatwise together until the tension of the spring overcomes thefused or partlyfused film of solder and moves that one of the plateswhich is fast to the spring away from the other plate in a line normalto the film of solder, as more fully explained below.

In the drawings, Figure 1 is a cross-section of one of my thermostatscomplete. Fig. 2 is a bottom plan of the upper part of Fig. 1. Fig. 3 isa modification.

In the preferred form of my thermostat shown in the drawings, A is aspiral spring whose abutments B B are connected when the spring A isunder compression by a film of solder O, fusible at the desiredtemperature between plates B and C, so that when plate O is suitablyconnected to abutment B the compression of spiral spring A depends uponthe film of solder 0 between plate B and plate 0, which prevents thoseplates B and C from flying apart under the force of spiral spring A, sothat when the film of solder G is fused one of the abutments, in thiscase B, is carried by the spiral spring A directly away from the otherabutment and in a direction normal to the planes of both abutments andof the film of solder and makes contact between electrodes E E orotherwise, either electrically or mechanically, shows that thetemperature has risen to the fusing-point of solder 0 and that solder Ohas melted or so softened by heat that the spiral spring has beenreleased and has forced the abutments apart by a strain directly acrossthe film of solder instead of in a line parallel with that film, asheretofore. This operation of my thermostat under a given rise oftemperature injures no part of my thermostat except the film of solder,so that my thermostats after one operation can be refitted for a seconduse by simply resoldering plate B to plate 0.

One use of my thermostat is as an automatic circuit-closer, and in orderto adapt my thermostat for ready use for this purpose 1 provide a cap Fand base F of a dialectric, commonly porcelain, which forms a holderformy thermostat and also for the electrodes E E, which are inelectrical connection with the wires to w, carried by the binding-postsd d, as will be clear from the drawings without more detaileddescription.

As it is desirable to carry plate B well clear of the holder F F,especiallyin order to prevent heat radiating from it to its holder, Iuse a sleeve G of fiber or other good heatinsulator between abutment Band that part of cap F on which one end of spring'A directly bears andin this way make my thermostat almost perfectly sensitive, for if itwere not for this heat-insulating sleeve G the rise in temperature ofthe air about the outer surface of plate .B must be sufficient to bringnot only plate B, but practically its holder F F and spring A and theother abutment B, each and all, to the temperature required to fuse ornearly fuse the film of solder O, whereas when plate B is insulated fromthe chilling effect of the other parts my thermostat is much moresensitive than when the spiral spring A bears directly on plate B andplate B bears directly on cap F.

In the modification shown in Fig. 3 my thermostat is movable in order toact as a push-button, as will be plain without further description.

Other uses of my thermostat are described in my application filedOctober 28, 1902, Serial No. 129,133.

The heat-insulating sleeve G is a second feature of my invention of muchpractical importance, as it enables me to provide thermostats closelyadjusted to operate at widelydiiferent temperatures by simply using asolder O fusible at the required temperature, whereas in all thermostatsheretofore made the chilling effect of the holder and other parts had aninfluence which made it practically impossible to determine what solderto use in order to insure the prompt action of the thermostat under allconditions of rising temperature when the predetermined temperature isreached, which is the main object of my invention and attained with aclose approach to accuracy by using a film of solder O to connect thetwo plates B and C, holding a spiral spring under compression, and withstill greater accuracy by using also the sleeve G to protect the film ofsolder C between the plates from the chilling effect of contiguousparts.

In Fig. 1 there are two springs tending to separate B and B. This iswholly new with methat is, E is a leaf-spring as well as an electricconnection between 10 and d, on the one hand, and B, on the other, andthat leafspring E tends to carry B into contact with E, and the spiralspring A reinforces E as a spring and makes it certain that whether E beset or notthat is, whether it be weak or strong or act to preventcontact between B and Eyet the spiral spring A will cause that contactwith certainty. I

What I claim as my invention is- The improved thermostat above describedcomprising the holder F of electric insulating material; the sleeve G;the plate B supported on the sleeve G; the plate 0 within the sleeve G,and connected with plate B by a fiat film G of fusible solder; thespiral spring A, one abutment B of which is connected to plate 0 by rodD; and electrodes E E which are brought into electric contact by themotion of abutment B, all substantially as described.

GEORGE AUGUSTUS WALL.

Witnesses:

(J. B. .MAYNADIER, G. A. ROCKWELL.

